http://nova.newcastle.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:1805 A major role has been postulated for a maintained increase in the autonomous activity of CaMKII in the expression of long-term potentiation (LTP). However, attempts to inhibit the expression of LTP with CaMKII inhibitors have yielded inconsistent results. Here we compare the changes in CaMKII autonomous activity and phosphorylation at Thr²⁸⁶ of αCaMKII in rat hippocampal slices using chemical or tetanic stimulation to produce either LTP or short-term potentiation (STP). Tetanus-induced LTP in area CA1 requires CaMKII activation and Thr²⁸⁶ phosphorylation of αCaMKII, but we did not observe an increase in autonomous activity. Next we induced LTP by 10 min exposure to 25 mm tetraethyl-ammonium (TEA) or 5 min exposure to 41 mm potassium (K) after pretreatment with calyculin A. Exposure to K alone produced STP. These protocols allowed us to monitor temporal changes in autonomous activity during and after exposure to the potentiating chemical stimulus. In chemically induced LTP, autonomous activity was maximally increased within 30 s whereas this increase was significantly delayed in STP. However, in both LTP and STP the two-fold increase in autonomous activity measured immediately after stimulation was short-lived, returning to baseline within 2–5 min after re-exposure to normal ACSF. In LTP, but not in STP, the phosphorylation of αCaMKII at Thr²⁸⁶ persisted for at least 60 min after stimulation. These results confirm that LTP is associated with a maintained increase in autophosphorylation at Thr²⁸⁶ but indicate that a persistent increase in the autonomous activity οf CaMKII is not required for the expression of LTP. 2010-04-27T06:11:21.247Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:1080 Measurement of the proportion of calcium/calmodulin-stimulated protein kinase II (CaMPK-II) that is autonomously active or phosphorylated on Thr286 is thought to provide an index of the degree to which CaMPK-II in a tissue has been activated. We have examined how various ways of handling hippocampal tissue can alter these properties. Both autonomous activity and phospho-Thr²⁸⁶ content was high in freshly dissected hippocampus or freshly cut hippocampal slices. After incubation of hippocampal slices in artificial cerebrospinal fluid for 120 min, both properties of CaMPK-II decreased to a steady state level. Freeze–thaw or cutting the equilibrated slices could rapidly increase both autonomous activity and phospho-Thr²⁸⁶ immunoreactivity of CaMPK-II. These increases were comparable to changes induced by experimental treatment. Therefore, our results suggest that considerable care needs to be taken over the way in which hippocampal slices are handled. 2010-04-27T06:06:37.639Z ]]>